This is done using the register PINx where x is the register being read from. With our DDR register sorted out, its time to learn how to read digital values into our microcontroller from the real world. How about something more complex? Letâs say you want the first two pins to be outputs (PB0 and PB1), and the rest of the pins to be inputs. If we wanted to turn all the pins on PORT B into input pins then we could use. While it is common practice to use hexadecimal, the binary version can make it more clear which bits in the port are being used as an input or output. The first example uses hexadecimal, whereas the second uses binary. So letâs say if we want to configure all the pins on PORT B as outputs, we would simply use the following code: In PIC devices, a value of 1 is used for inputs and a value of 0 is used for outputs, but for AVR devices the reverse is true 1 refers to an output while 0 refers to an input. The DDR register is 8 bits long and each bit corresponds to a pin on that I/O port.įor example, the first bit (bit 0) of DDRB will determine if PB0 is an input or output, while the last bit (bit 7) will determine if PB7 is an input or output. The data direction register (DDR) is most likely the first register that you configure since the DDR register determines if pins on a specific port are inputs or outputs. In fact, an Arduino is just an AVR microcontroller with some special boot loading code and a USB-to-serial converter.īelow is the internal architecture of a typical ATmega device (in our case, the ATmega168). Another issue with AVR devices is their difficulty in chip programming (as compared to the PICKIT3 for example) if an official programmer is not purchased.ĭespite this, the AVR has become one of the most popular microcontrollers available thanks to the invention of the Arduino, which contains an ATmega at its heart. However, AVR devices are particularly prone to bricking when users start to play with the fuses (specific chip options), which is why it is highly recommended that you have multiple AVR devices on hand. Also, the AVR core has over 130 instructions, many of which are single-cycle (thanks to the one level pipeline), and there is no banking scheme. However, despite being a RISC CPU, the AVR core is arguably very powerful and has many advantages over competitor devices (such as the Microchip PIC range).įor example, the AVR core contains generic 8-bit registers that can be paired to create 16-bit pointers for memory locations. At the heart of most ATmega devices is the AVR CPU, which is described as a RISC-type CPU.
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